Inkjet printers have a series of nozzles from which individual ink droplets are ejected to deposit on print media to form desired printed images. The nozzles are incorporated in various types of print heads and their proper functioning is critical to the creation of quality images. Thus, any partial or total blockage of even a single nozzle may have a significant impact on a printed image, particularly in the case of a pagewidth printer.
The nozzles are prone to blockage due to their exposure to ever-present paper dust and other particulate matter and due to the tendency of ink to dry in the nozzles during, often very short, idle periods. That is, ink which is awaiting delivery from a nozzle forms a meniscus at the nozzle mouth and, when exposed to air, the ink solvent is evaporated to leave a nozzle blocking deposit.
Servicing systems are conventionally employed for maintaining the functionality of print heads, such systems providing one or more of the functions of capping, purging and wiping. Capping involves the covering of idle nozzles to preclude exposure of ink to drying air. Purging is normally effected by evacuating a capping chamber, thereby sucking deposits from the print head that block or have the potential to block the nozzles. Wiping is performed in conjunction with the capping and/or purging functions and involves gently sweeping a membrane across the face of the print head.
The majority of conventional Inkjet printers employ a reciprocating carriage which carries a print head (often in the form of a cartridge) and which is driven to traverse across the width of a momentarily stationary page or portion of print media. In these printers, service stations are provided at one side of the printing zone and, on command, the print head is traversed to the service station where it is docked for such time as servicing is performed and/or the printer is idle.
The above described servicing system cannot feasibly be employed in relation to pagewidth printers which, as above mentioned, have a stationary print head assembly that extends across the full width of the printing zone. The print head assembly effectively defines the print zone and it cannot be moved outside of that zone for servicing. Furthermore, a pagewidth print head has a significantly larger surface area and contains a vastly greater number of nozzles than a conventional Inkjet print head, especially in the case of a large format printer, all of which dictate an entirely different servicing approach from that which has conventionally been adopted.